The present invention relates to a method and arrangement in a telecommunications system, in particular it relates to a method and apparatus for automatically determining neighbor cells in a wireless telecommunication system.
For LTE (Long Term Evolution) telecommunication systems the concept self organizing network is currently being developed. At X2 setup, information about cells served under an eNB (evolved Node B), sometimes called base station or radio-base-station, is mutually exchanged. After that there is a procedure to determine which cells are actually neighboring cells.
The eNBs are usually interconnected with each other by means of an X2 interface. It is assumed that there always exist an X2 interface between the eNBs that need to communicate with each other, e.g. for support of handover of UEs in LTE_ACTIVE. The eNBs are also connected by means of the S1 interface to the EPC (Evolved Packet Core). The S1 interface supports a many-to-many relation between aGWs (Access Gateways) and eNBs. It should be noted that other interfaces may be used for the communication between the eNBs other than the X2 interface.
Currently a cell is defined a neighboring cell if it is manually configured and stored as a white listed cell, or if it is discovered by the ANRL (Automatic Neighbor Relation) function, i.e., a UE (User Equipment), sometimes also called mobile station or mobile terminal, finds the cell while performing measurements in active state.
One problem with waiting for a UE to perform measurements in order to find neighboring cells is that a UE will normally not measure on inter frequency or inter-RAT cells unless explicitly informed to do so by the eNB. The UE will need measurements gaps to do so and the gaps imply performance loss. Another problem is that the eNB might not be aware of which neighbor frequencies it shall request UEs to perform interfrequency measurements.
Therefore there is a need in the art to provide a solution that alleviates the above indicated problems.